The present disclosure relates to an imaging apparatus and an image transmitting method used in the same, and more particularly to an imaging apparatus for which a cost of parts or components can be reduced, and an image transmitting method used in the same.
Heretofore, analog transmission in which a video signal obtained from a monitoring camera is transmitted as an analog signal to a Camera Control Unit (hereinafter referred to as “a CCU”) through a coaxial cable has been a mainstream in a monitoring camera system. The popularization of the analog transmission is wide and thus in a facility to which a monitoring camera system is introduced, cables are laid so as to penetrate in every hole and corner of the facility.
Although in recent years, there has been desired the increasing in the image quality of an image due to the digitization, a great cost is required for replacement of the cables which are laid so as to penetrate in every hole and corner of the facility.
In an image transmitting system used to transmit a video signal through a coaxial cable, there are proposed a technique adapted to transmit a digital signal, and a technique adapted to transmit a digital signal together with an analog signal. These techniques, for example, are described in Japanese Patent Laid-Open No. 2010-251979 and PCT Patent Publication No. WO 2010/88625.
FIG. 1 shows an example of a configuration of an image transmitting system used to transmit both of an analog signal and a digital signal through a coaxial cable.
In the image transmitting system shown in FIG. 1, a camera 1 generates both of a digital video signal and an analog video signal as a video signal of a captured moving image, and transmits both of the digital video signal and the analog video signal to a CCU 3 through a coaxial cable 2. The CCU 3 transmits a control signal in accordance with which the camera 1 is controlled to the camera 1 through the coaxial cable 2. It is noted that the video signal which has been transmitted to the CCU 3 is supplied to a recording apparatus or a reproducing apparatus (both not shown) and is then recorded or reproduced (displayed).
In the system used to carry out the existing analog transmission, a frequency band of an analog signal to be transmitted is in the range of about 0 Hz (DC (Direct Current)) to 10 MHz, and thus a frequency band above 10 MHz is not used at all. Then, in the image transmitting system shown in FIG. 1, as shown in FIG. 2, a band (in the range of about 10 MHz to 100 MHz) above the frequency band with which the analog video signal is transmitted is also utilized, whereby it is realized to transmit both of the digital video signal and the control signal in addition to the analog video signal.
FIG. 3 is a block diagram showing an example of a concrete configuration of the camera 1 shown in FIG. 1.
In the camera 1 shown in FIG. 3, a signal processing portion 22 subjects a video signal acquired from an imaging portion 21 to predetermined processing, and supplies the resulting video signal to each of a coding portion 23 and a CVBS conversion portion 27.
The coding portion 23 compression-codes the video signal supplied thereto from the signal processing portion 22 in accordance with a Moving Picture Experts Group (MPEG) system and supplies the coded signal to a modulating portion 24. The modulating portion 24 modulates the coded signal supplied thereto from the coding portion 23 in accordance with an Orthogonal Frequency Division Multiplexing (OFDM) system, and supplies the modulated signal to a D/A conversion portion 25. The D/A conversion portion 25 subjects the modulated signal obtained through the modulation in the modulating portion 24 to Digital to Analog (D/A) conversion and supplies the resulting signal to a filter processing portion 26. The filter processing portion 26 extracts only a component in a predetermined frequency band from the signal supplied thereto from the D/A conversion portion 25, thereby carrying out band limitation, and supplies the resulting signal to an adder 30.
The CVBS conversion portion 27 converts the video signal supplied thereto from the signal processing portion 22 into a digital composite video signal (Composite Video, Blanking, and Sync (CVBS) signal) in accordance with D2-VTR (D2-Videotape Recorder), and supplies the CVBS signal to a D/A conversion portion 28. The D/A conversion portion 28 subjects the CVBS signal obtained through the conversion in the CVBS conversion portion 27 to D/A conversion, and supplies the resulting signal to a filter processing portion 29. The filter processing portion 29 extracts only a component in a predetermined frequency band from the signal supplied thereto from the D/A conversion portion 28, thereby carrying out band limitation, and supplies the resulting signal to the adder 30.
The adder 30 adds the signal (digital video signal) supplied thereto from the filter processing portion 26, and the signal (analog video signal) supplied thereto from the filter processing portion 29 to each other, and a signal sending portion 31 sends the signal obtained through the addition in the adder 30 to the coaxial cable 2.
It is noted that in the camera 1 shown in FIG. 3, a configuration adapted to receive the control signal supplied from the CCU 3 is omitted here in illustration and description thereof for the sake of simplicity.
With such a configuration, the camera 1 can transmit both of the analog video signal and the digital video signal to the CCU 3 through the coaxial cable 2.
In the CCU 3, the analog video signal supplied from the camera 1 shown in FIG. 3 is either recorded or reproduced with a lower delay than that in the digital video signal. The digital video signal is either recorded or reproduced at a higher image quality than that in the analog video signal. That is to say, by applying the image transmitting system shown in FIG. 1 to the monitoring camera system, when a watcher chases a suspicious individual, the watcher can control a monitoring camera while he/she visually checks the small-delay analog image, and also can record the high-quality digital image.